Induction furnace



Aug. 14, 1928. 1,680,407

P. H. BRACE INDUCTION FURNACE Filec} Aug. 29, 1927 WITNESSES: INVENTOR Porter HBraae.

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Patented Aug. 14, 1928.

PORTER H. IBRACE, OFWILKINSBURG,

PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING GOMPAN Y, A CORPORATION OF PENNSYLVANIA.

rnn'ucrron FURNACE.

Application filed August 29, 1927. Serial No. 216,153.

.My invention relates to electric furnaces and more particularly-to furnaces of the induction type.

In coreles's, or ironless, induction furnaces, v

operable on relatively low frequency alternating current of the order of 60 cycles per second, it is necessary to energize the 1nductor coil at rather a high current density with resultant high 1 R losses. It becomes necessary therefore, inductor coil, and this is usually accomplished by making the coil of tubing to rovide a passage for the flow of a cooling uid therethroug Since the inductor coil completely surrounds the charge, the greater portion of the heat lost by the charge is also absorbed by the cooling fluid and carried off.

It is an object of my inventiomtherefore, to provide, in combination with a fluid cooled inductor coil, means for converting the heat absorbed by the cooling fluid into electrical energy, and for returnin the electrical energy to the circuit of the inductor coil.

Another object of my invention is to provide means operated by the heat energy contained in the cooling fluid effluent from a fluid cooled inductor coil, for correcting the inherently unfavorable power factor of the furnace.

In practicing my invention I provide, in conjunction with an induction furnace employing a hollow'water cooled inductor coil, a complete mechanical circuit for the cooling water outside the furnace which directs the water from the coil successively through a steam turbine, a condenser, and a centrifugal pump back to the input end of the coil; The steam turbine is operatively connected to a synchronous generator which, in

turn, is electrically connected in parallel energy with the main source of electrical for the inductor coil.

In the drawing, the single figure shows an induction furnace in vertical section and a schematic showing of the elements and mechanism employed in conjunction therewith for carrying out my invention.

Referring more particularly to the drawing, an ironless induction furnace, indicated broadly as 1, comprises a shell or casing 2 of suitable refractory heat-insulating material, and a crucible 4 coaxial therewith and supported in spaced relation with the inner face thereof. In the space between the cruto artificially cool the v operatively connected to cible 4 and casing 2v is positioned a substantially helical inductor coil 6 embedded in a quantity of granular refractory material 8, completely filling said space. The inductor coll 6 is formed of'flattened copper tubing to provide a passage therethrough for a 0001- mg fluid as hereinafter described. The top of thefurnace isclosed by a removable cover- 10 in the usual manner.

Since theparticular details of-the furnace structure form no part of the present invention, further description thereof is not deemed necessary. 7

Inlet and outlet conduits 12 and 14 respectively, for supplying a cooling fluid,

preferably water in the present embodiment,

to theinductor coil, extend through the side wall of the casing 2 and operatl-vely 'communicate with the ends of the hollow coil 6.

Conduit 14 terminates in a flange 16 which is adapted to be. clamped to a flange 17 on a section of conduit 18 communicating with a thermostatically controlled valve 22, to provide apassage for the cooling fluid therethrough. Between the cooperatin faces of flanges 16 and 17 is an aperture plate 20 of suitable electrical insulating material, for breaking the otherwise complete electrical circuit afforded by the mechanical circuit for the cooling fluid, as hereinafter described.

The valve 22is operated in accordance with the temperature of the cooling fluid by means of any well-known type of thermally responsive mechanism 24 operatively connected to the stem of valve 22. i

A conduit 26 connected to the other side of valve 22 communicates with the inlet ,openin of a steam turbine 28 which is operable .1n the usual manner by steam efiluent therefrom.

From the exhaust side of turbine 28 the coolin fluid is conducted through a conduit 30 and steam condenser 32, conduit 34 and motor driven centrifugal pum 36 and conduit 38 back to the inlet conduit 12 which is conduit 38 by means of a coupling 40.

A complete and a continuous assa e for the cooling water is thereby a orde connecting the two ends of the inductor coil.

As indicated in the drawing, the showing of the thermostatically controlled valve, the steam turbine, the condenser and centrifugal pump are merely diagrammatic, and since elements in common commercial usage, a further and more detailed d escription thereofis not necessary. Quite obviously, additional means in the fluid C11- cuit may be added as found necessary for varying operating conditions. For example, it may be desirable to employ traps to separate the steam and water, and to incorporate a pressure responsive means in the fluid circuit to protect the coil. (Ihe employment of such means, if desired, is obvious to one skilled in the art, and therefore the illustration and description thereof is not deemed necessary.

The rotor of the steam turbine 28 is operatively connected through a suitable couthey are all pling 42 to a synchronous generator 44 driven thereby.

Energization of coil 6 is effected by a suitable source of commercial frequency alternating' current (not shown), through leads 50 and 52*c onnected to the coupling 40 and flange 16, respectively. A flux is thereby induced in the metallic charge in crucible 4, and the charge is heated and melted in the usual manner.

The synchronous generator 44 is electrically connected through leads 54 and 56 to the coupling 40 and flange 16, respectively, so that the electrical energy generated thereby is returned to the circuit of the inductor coil.

The centrifugal pump 36 is driven by an electrical motor 58 connected across the leads 50 and 52 for continuous operation 00'- incident with the operation of the furnace, as indicated.

In operation upon the energizat-ion of coil 6, the coo ing fluid contained therein is heated responsive to the PR loss in the coil and the heat lost from the charge in crucible 4, and a sufficient temperature will be attained to form steam therein. When the steam has attained a desired temperature the valve 22 is automatically opened responsive to the action of the thermal control device 24, and the steam passes into the turbine 28 to cause the operation thereof and the consequent operation of the synchronous generator '44. 4

The steam then is conducted through conduit 30 into condenser 32, where it is reduced to a liquid state, and from 'thence through the centrifugal pump 36 back into the inductor coil.

The operation of the synchronous generator 44 converts the mechanical energy of the turbine into electrical energy, and supplies the electrical energy to the terminals of the inductor coil. The generator thereby serves to supply the wattless component'of the inductor current which tends to correct the unfavorable power respect to the primary electrical power supfactor of the furnace with r By my invention I have devised a means for recovering a large portion of the waste heat from a water cooled inductor coil at a relatively slight increased investment in apparatus. The temperature of the cooling fluid is automatically reduced during its expansion into steam and passage to the turbine, but the heat remaining inthe water is not lost since it merely tends to increase the rate of circulation required to maintain the desired outlet temperature, thereby increasing the amount of steam supplied to the turme. While I have shown and described a particular combination of elements for converting the heat energy of the cooling water into electrical energy, it "s clearly within the scope of my invention to use various other combinations and arrangements of elements for effecting the desired results.

'Modifications may be made in tion without departing from the scope thereof and I- desire, there ore, that only such limitations shall be placed thereon as are imposed by the prior art and set forth in the appended claims. I claim as my invention: 1. In an induction furnace,

my invenmeans for converting the heat energy 0 steam eflluent from said coil into electrical energy, and means for returning said electrical energy to the electrical circuit of said inductor coil.

2. In an induction furnace, the combination with a water-cooled inductor coil, of means for converting the heat energy of steam eflluent from said coil into electrical energy, comprising a steam turbine mechanically cooperating with said inductor coil an electrical generator driven thereby, an means for electrically connecting said generator with said inductor coil.

3. Inan induction furnace, the combination with a water-cooled inductor coil and an energizing circuit therefor, of means for correcting the power factor of said coil, com- 1 generator" electrically connected across said ener ing' fient prising a synchronous electrical circuit, and means operated by steam e from sa d coil for driving said enerator.

4. In an induction furnace, t e combinatlon with a hollow, water-cooled, inductor coil and an energizing circuit therefor, of means for supplying a leading current to said 0011, comprising asynchronous enerator electrically connected to the terminals of sa d 0011, and means responsive to steam efliuent fromsaid coil for driving said generator, COIDPI'lSlIlg a steam turbine operatively connected to the exhaust end of said 001 5. In an induction furnace, the combina-.-- tlon with a water-cooled inductor coil and an energizing circuit therefor, of means for s irit and.

the combina tion with a water-cooled inductor coil, of f supplying a leading current to said coil, comprising a synchronous generator electrically connected to the terminals of said coil, and means responsive to steam efliuent from said coil for driving said generator, comprising a steam turbine operatively connected to the exhaust end of said coil, and thermostatic means between said coil and turbine for controlling the flow of steam therethrough.

6. In an induction furnace, the combination with a hollow induction coil and means for energizing the same, of a complete mechanical circuit, connecting the ends of said coil providing a path for the circulation of cooling water therethrough, and including in series a steam turbine, a condenser, and a pump, whereby steam efliuent from the exhaust end of said coil operates said turbine,

is condensed in said condenser, and forcedback into the coil inlet by said pump, and a synchronous generator driven by said turbine and connected electrically in the circuit of said inductor coil, in parallel therewith.

In testimony whereof, I have hereunto subscribed my gust, 1927.

PORTERH. BRACE.

name this 19th day of Au- 5 

